The present invention relates generally to mechanisms for tuning or detuning a stringed musical instrument. Specifically, the invention relates to a mechanism for changing the pitch to create vibrato effects and other pitch variations in a stringed musical instrument. The invention also relates to a mechanism for reducing transmission of vibration noise between bridge and other components of tuning devices for stringed musical instruments.
A tremolo mechanism functions by changing the tension of all of the strings of an instrument simultaneously to create a pitch change during playing of the instrument to create a vibrato sound. As used with electric guitars, a tremolo mechanism typically incorporates a tailpiece pivotally joined to a base support mounted on the body of the guitar. A tuning assembly attached to the frame of the tailpiece is utilized to anchor the end of each of a plurality of tensioned strings strung over the guitar's bridge. In such a mechanism, a counter spring is utilized to counteract the reactive bias of the plurality of tensioned strings upon the tailpiece. A tremolo arm is connected to the tailpiece for pivoting of the tailpiece about the base while simultaneously playing the instrument.
A significant problem with such tremolo mechanisms regards to the pitch relationship between the individual strings. In earlier devices, all strings of the instrument are moved the same distance when the mechanism is actuated. Since the higher pitched strings of the instrument generally have much greater elasticity than the lower strings, the lower pitched strings exhibit a greater change in pitch for a given change in string length. For example, if a chord is played on the instrument, and the tremolo mechanism is actuated, the length of each string changes an equal amount. The low pitched strings of the instrument detune (i.e. change pitch) more than the high pitched strings, and the pitch relationships within the chord are lost.
The insufficiency of conventional tremolo mechanisms in maintaining pitch relationships as the tailpiece is pivoted during instrument play has been recognized by inventors in the prior art. An example of a tremolo mechanism adapted to maintain pitch relationships is shown in one of the present inventor's prior patents, U.S. Pat. No. 4,632,005 (the '005 patent) issued to Steinberger on Dec. 30, 1985, entitled “Tremolo Mechanism for an Electric Guitar.” The '005 patent teaches use of a roller bridge disposed atop a base mounted on the body of a guitar. The roller bridge includes a plurality of saddle rollers assembled on a support surface of the base. A plurality of anchor devices are slidably mounted on a plate providing a second support surface mounted on the tailpiece frame. The anchor devices are each aligned parallel with the axis of the tensioned string strung across a corresponding saddle roller and anchor the end of the tensioned string. The anchor device includes a slotted cylindrical bore adapted to hold a disc shaped ball affixed to the end of the tensioned string. Each anchor device is connected to a spring-biased threaded rod, which may be operated to position the anchor device longitudinally so as to adjust the pitch of such string.
The '005 patent teaches joining the tailpiece to the base by means of a detuning pivot having a pivot axis which is oblique with respect to the string plane defined generally by the plurality of strings. Thus, for a selected radial displacement of the tailpiece about the pivot axis, the string ends of the individual strings are moved varying distances with respect to the corresponding bridge roller so as to generally preserve the pitch relationships between the strings as the tremolo device is employed.
Although a significant step in the art of preserving pitch relationships as the tremolo mechanism is used during guitar play, the device of the '005 patent has room for improvement. One issue encountered in using the mechanism is the tendency of the string end anchors to malfunction. Movement of the tailpiece causes changes in both the magnitude and direction of tension force exerted on the string end ball disposed in the slotted cylindrical bore of the anchor mechanism. Friction may cause the disc shaped balls to jam or cock in the anchor bore. Such jammed balls change the designed geometry of the bridge break angle and change the designed distance between the anchor point and the portion of string held in the bridge roller (herein termed “string apex”). Jammed balls may also become displaced from the bore or may suddenly slip from a jammed position to an aligned position during play. All of these malfunctions affect the amount of change in string length between the anchor mechanism and the bridge, and thus affect the pitch of the string.
Accordingly, what is needed is an apparatus that provides for the alignment of the anchor, string end and the string apex. Such alignment apparatus should react continuously, rapidly and without detectable frictional effects as the tremolo mechanism is displaced through its designed range of rotational freedom relative to the detuning axis.
An additional problem common to roller bridge mechanisms such as the tremolo mechanism of the '005 patent is vibration noise transferred from an oscillating string to the roller mechanism and therefrom to adjacent roller mechanisms and strings. When a guitar string is plucked and released, the string vibrates in multiple directions in the transverse plane. A string vibrating within the roller seat causes the roller to vibrate as well. Since the roller is connected to the saddle block via a roller pin press-fitted through the roller, components of string vibration that are parallel to the roller pin cause the roller and roller pin to vibrate axially within the bores of the saddle block wall. Vibrations within the saddle block wall are transmitted to adjacent saddle block walls and to other bridge components. This vibrational “cross-over” noise is detrimental to the acoustic characteristics of the instrument. Thus, it is highly desirous that a means of eliminating such “cross-over” noise be incorporated into tremolo mechanisms as well as in general roller bridge mechanisms.
Accordingly, what is needed is an apparatus that prevents axial vibration of such roller and roller pins within the bores of saddle blocks of saddle rollers. Such apparatus should minimize the frictional effects of noise suppression and not interfere with the roller function in supporting the tensioned string.
A third disadvantage of the tremolo apparatus of the '005 patent is its limited combination of locking positions and the inability of it and other prior art tremolo mechanisms to provide a plurality of locked positions separated tonally by only the smallest chromatic intervals. The '005 patent teaches that the lock is positioned about the longitudinal midpoint and on one side of the tailpiece frame. The lock is operated by means of the handle for positioning a locking bar in one of three (3) locking seats that are disposed on an extending rod and in opposition to the locking ridge. The lock has only one locking position wherein the lock prevents displacement of the tailpiece frame from the seat in either direction of rotation about the detuning axis (herein termed a “positive control” locking position). This is accomplished in the '005 patent apparatus by placing walls or stops on either side of the central seat of the locking mechanism so as to create a channel to receive and hold the locking bar. The lock has two additional locking positions, one on either side of the central locking channel. The additional locking positions have only one stop that is disposed between the locking position seat and the central seat. Displacement in the opposite direction of rotation is prevented by the counter bias of the counter spring holding the locking ridge against the stop.
The method of tuning the stringed instrument of the '005 patent requires that the tremolo mechanism be first locked in the central locking seat. The individual strings are then tuned and the tremolo mechanism is unlocked. Tune is restored by adjustment of the counter spring. The result is that the tailpiece frame in its equilibrium position is necessarily generally aligned with the radial position of the tailpiece frame corresponding to that when the lock is locked in the central channel. The tremolo device of the '005 patent can adjust pitch up or down only one full chromatic step by engaging the lock in the corresponding additional locking positions.
Additionally, the lock of the '005 patent is very sensitive to any deviation from an intermeshing alignment of the component parts of the lock as the lock is placed in a locking position. Because the locking components are rigidly connected, an exact intermeshing of the component parts is necessary for the lock to function properly. While continuing to play the instrument, the user must properly first operate the handle as a lever to deflect the tailpiece to very closely align the locking components and then rotate the handle to engage the locking components. Not surprisingly, misalignments are common and may prevent the lock from locking or may damage a lock component.
Accordingly, what is needed is a tremolo lock mechanism that provides for tuning of the instrument such that the tailpiece frame may be aligned in any of a plurality of equilibrium positions, each corresponding to one of a plurality of positive control locking channels. Such a tremolo device should be capable of adjusting the pitch of the strings by any of a plurality of half chromatic steps by engaging the lock in corresponding locking positions.
Additionally, what is needed is a tremolo lock mechanism that accommodates misalignment of intermeshing component parts during the process of locking while neither failing to lock nor damaging a lock component.
Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description or will be learned by practice of the invention.